Previously, probe fixtures for testing semiconductor wafers have been limited to devices utilizing long unsupported needles on solid metallic contact probes that are operable up to frequencies of approx. 1.0 megahertz. An example of this prior art is found in U.S. Pat. No. 4,195,259 issued to Reid et al. In this disclosure an angled probe tip is connected to a support sleeve attached to an extended arm. The flowpath for the signal is directed through lead wires to the electronic amplifier, discriminator, buffer, etc. to an evaluated display.
Kattner et al in U.S. Pat. No. 4,065,717 teaches a plurality of leads on a backing plate that is transparent and resilient. The ends of the leads are provided with raised portions which establish the probes, preferably formed by conventional thin film or plating techniques. A vacuum is pulled on the chip under test firmly securing it in place while pressure is applied above the resilient backing plate causing deformation to occur, moving the probes into contact with the workpiece.
U.S. Pat. No. 3,867,698 issued to Beltz et al discloses a plurality of leads simultaneously bent into a truncated shape. The probe fingers are an extension of the lead, as above, but are formed at the same time with a conventional die set after the leads are secured in a plastic material. The fingers or probe tips are separated by severing with a sharp instrument. Further, the leads may be lapped to impart to them the desired degree of flatness and smoothness as to not damage the semiconductor beam leads on which they rest during probing.
P. V. N. Heller teaches in U.S. Pat. No. 3,560,907 an arrangement whereby a plurality of individual flexing arms are apportioned in a circular array. The flexing arms are spring loaded to provide resiliency with wire leads connected on the outside periphery of the enclosure to terminal posts for transmitting the electrical signal. The contact point that is contiguous with the workpiece is integrally formed with the connector contact which engages a prescribed point in the circuit, thereby permitting the conducting of measuring circuit response by external equipment.
Finally, U.S. Pat. No. 4,045,737 issued to Coberly discloses a similar arrangement where a plastic substrate is provided with a groove in which an electrically conductive contact or probe is positioned within a key portion. The probe contains a pair of cantilevers which bias against the edge of the substrate providing a planarity stop serving as vertical alignment. The bias produced by the cantilevers is overcome and a flat raises upwardly from the edge of the substrate as the point touches the chip. The electrical conductive flowpath is continued from the probe via a wire lead to a binding post and, hence, to collateral test apparatus.
While the prior art addresses the problem of compliance and provides an electrical flowpath for frequencies up to 1.0 megahertz using conventional wires and conductive structure, it is still lacking in structure that is capable of conveying signals of higher frequency. As different means to conduct microwave signals are required, such as coaxial cables and isolated flowpaths, prior art has apparently not as yet delved into the discipline dealing with frequencies of over 500 megahertz.
For background purposes and as indicative of the art to which the invention relates, further reference may be made to the following U.S. patents.
______________________________________ No. 4,365,195 Stegens December 21, 1982 No. 4,101,824 Breedlove et al July 18, 1978 No. 3,775,644 Cotner et al November 27, 1973 ______________________________________